1. Field of the Invention
The present invention relates to improvements in a roller bearing using cylindrical rollers as rolling elements.
2. Background Art
A roller bearing using cylindrical rollers as rolling elements has often a thrust load, as well as a radial load, and has a structure in which a flange portion is provided on an outer circumferential face end part of an inner ring and an inner circumferential face end part of an outer ring, and an end face of a cylindrical roller is contacted with an inner side face of the flange portion to receive the thrust load. However, if the cylindrical roller is rolling while the rolling contact surfaces of rolling elements of the inner ring and the outer ring are skewed, an edge part of the cylindrical roller contacts the inner side face of the flange portion, causing a shorter life of the bearing. For this reason, the inner side face of the flange portion is inclined at a predetermined opening angle to the end face of cylindrical roller in the roller bearing, as described in JP-A-7-12119, for example.
In this roller bearing, when the cylindrical roller is skewed, an edge part of the cylindrical roller is prevented from contacting the inner side face of the flange portion. However, when the cylindrical roller is not skewed, an end face of the cylindrical roller contacts a grinding clearance groove of the inner ring and/or the outer ring, producing an edge load to cause a premature wear, when subjected to a thrust load. Thus, to suppress the occurrence of edge load, the roller bearing has been offered in which a peripheral part of end face of the cylindrical roller is crowned like circular arc at a single curvature (refer to JP-A-2002-70874).
However, if the peripheral part of end face of the cylindrical roller is crowned like circular arc at single curvature, the contact position between cylindrical roller and flange portion is greatly changed with the opening angle of the inner side face of flange portion. Therefore, the roller bearing as described in JP-A-2002-70874 is required to manufacture by setting up the opening angle of the inner side face of flange portion strictly to keep the contact position between cylindrical roller and flange portion invariable, causing the increased cost. Since the roller bearing as described in JP-A-2002-70874 has a narrower clearance formed between the end face of cylindrical roller and the inner side face of flange portion with the contact position between the cylindrical roller and the flange portion therebetween, the lubricant such as grease is difficult to permeate, resulting in a problem that seizure is more likely to occur.